Dresden 2014 – scientific programme

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BP: Fachverband Biologische Physik

BP 17: Microswimmers (joint DY/BP)

BP 17.4: Talk

Tuesday, April 1, 2014, 10:15–10:30, ZEU 146

Optimization of bead-spring micro-swimmers and study of dense swimmer solutions — •Jayant Pande^1,2 and Ana-Sunčana Smith^1,2 — ¹Institute for Theoretical Physics, Friedrich-Alexander University, Erlangen, Germany — ²EAM: Cluster of Excellence, Friedrich-Alexander University, Erlangen, Germany

With the increasing need to understand and predict the locomotion of natural organisms and machines at the micro-scale, the theoretical modelling of micro-swimmers has become an important field of study. Contributing to its development, we present analytical results on the geometric and kinematic optimization of three-ellipsoid micro-swimmers, based on the three-sphere model of Najafi and Golestanian. Assuming a sinusoidal driving protocol, we identify different drag-related regimes and determine the exact shapes which maximise the swimming velocity and efficiency in each regime. Conditions on the optimal forcing parameters as well as the push/pull nature of the swimmer are elucidated. The analytical work is supported by simulations using an in-house framework based on the lattice-Boltzmann method. Its versatility and massively-parallel capabilities allow us to explore near-field effects as well as those arising from asymmetry in the swimmer design. We show that these effects, while inaccessible to an exact theoretical treatment, are nevertheless amenable to an approximate description. In the last part of our contribution, we employ our simulation system to study large populations of passive and active particles in fluids. For different concentrations, we observe previously-known effects as well as departures from theory.